There is an increasing interest in investigating the dynamic strength and impact characteristics of various vehicle components in the effort to enhance the crashworthiness features of those components. Actual full-scale crash tests to assess crashworthiness of vehicle components such as motorcycle or automobile wheels is expensive and space consuming since they require the use of sleds or moving barriers to simulate the impact. This is particularly inappropriate and unworthy when only a specific critical component of a vehicle is to be investigated, under varying impact conditions and great number of test parameters. In such a case, a laboratory component testing would be a better approach. It is to be emphasized that the laboratory impact simulation tests can never exactly duplicate the real-world impact conditions. However, it is important that any laboratory component impact test system is at least capable to simulate the essential and critical characteristics of impact experienced by structures in real-world conditions.
There are many different techniques for such low velocity but relatively high load simulation crash testing, in terms of propulsion being utilized to operate the impact test system such as gravity force, mechanical ram, explosive guns, etc. The gravity propelled type is the most commonly employed since a large percentages of crashworthiness studies lie within the limits of medium strain rate regime, with strain rate range from 0.1s−1 to 200s−1, which is within the capability of gravity propelled test system. The gravity propelled type also offers a cost effective advantage. Two types of gravity propelled impact machines are the drop weight and pendulum types. Such test systems are usually readily available from specialized suppliers with their performance and quality guaranteed. Among the shortcomings of such test system are expensive and may not suit the requirement of testing, the working space may be limited to a small test specimen. In contrast, when a pendulum or drop weight test rig is required by a laboratory, most of the laboratories will opt to carry out the design, development and calibration of the system in-house. This is because it is more economical and can be made to a desired degree of flexibility, working space and rigidity. This is especially true for development of heavy-duty special purpose impact test system. The major drawback of in-house fabrication is that expertise is highly needed in mechanical and electronic installation and commissioning to ensure a reliable performance.
However, pendulum type impact test rig offers several advantages compared to drop weight type. For a given drop height the pendulum will give the highest impact velocity providing the mass distribution is not biased heavily towards the fulcrum. Also, for the same drop height, the pendulum striker travels considerably farther and has almost constant velocity when it impacts the test item. Free-fall carriages have to be guided and thus the friction can vary not only due to binding during the actual free fall but also due to more severe binding after the striker hits the test item and creates some offset loading. Providing the pendulum uses ball bearings, the friction is negligible and constant throughout its travel. The relatively high friction of drop weight type striker also contributes to the lower velocity that can be achieved at similar falling height compared to pendulum type. A simple pendulum type impact test rig is simple to construct and can be accommodated easily in most commercial buildings with reasonable ceiling height. The free fall test rig requires expensive and rigid guidance equipment if binding is to be kept to a minimum. In terms of maintenance, a pendulum with just two self-aligning bearings is easy to maintain whereas free fall equipment with its guides and linear bearings is difficult to maintain.
One known heavy-duty pendulum impact test rig is that which developed for SAE J1981 standard for automobile wheel-tyre assemblies road hazard impact test. Test item is attached to a holding fixture which constructed of tubular upright part and cantilevered horizontal part. The test rig is capable of generating the rated maximum impact velocity of about 33 km/h and the maximum impact energy of about 1.6 kJ, corresponding to the maximum impact velocity. One of the disadvantages of this test rig is its relatively high deviation of center of percussion from the striker nose, or the impact region. Difficulties that would occur with this are:                (1) Shock will be transmitted back to the supporting frame, and this would causes erroneous readings of the impact value.        (2) The pendulum will be more susceptible to damage by bending or by fracture.        (3) The pendulum will absorb high deformation energy causing erroneous impact readings.        (4) The bearings will deteriorate rapidly.        
Another disadvantage is that the test rig does not provide flexibility for varying the striking weight. This characteristic is favourable to allow varying impulsive forces to be applied on the test component.
In another prior art light-duty pendulum impact test rig, the pendulum arm is constructed to extended above its pivot point by an amount equal to one-half of the stem length suspended below the pivot point so that the center of percussion will be located exactly at the center of the striking edge. In such condition, the pendulum portion that extended above the pivot point would become longer as the length suspended below the pivot point increases. The problem with this is it creates a laterally instability when the pendulum swings, which will cause a connection failure at pivot point and deteriorate the bearings that support the shaft. Also, it creates a significant moment at the extended portion that oppose to the striking moment which will reduce the effective velocity, force, and energy delivered.
Accordingly, the principal object of the present invention is to provide an economic yet reliable tool for performing frontal direct crash tests on motorcycle frontal components and impact tests for other vehicle components, which utilizes a large pendulum structure for generating the impact energy and impact velocity required. The further object of the present invention is to provide a impact test rig for crash testing other structural components. Another object of the invention is to developed a pendulum hammer with its center of percussion controllable in the vicinity of the striking region whilst allow for varying the striker location and striking weight. It is desirable to provide an impact test rig with large working space which would be able for placing a large structural test item such as a complete motorcycle. It is desirable to provide such a test rig which able to simulate critical characteristics of impact in real-world and full-scale crash test conditions.